Which organ appeared first?
Human gut microbiota
Dmitry Alekseev, Post-science
Microbiota is a new organ of the human body. To begin with, let's look at the origin of this organ and the history of its study. The intestine is the first organ that is associated with the appearance of our multicellular ancestors. It was like a tube: the entrance, exit, muscles and in the middle of the tube the intestine, in which bacteria lived. The intestines have an ideal environment for bacteria, because it is dark, warm and there is food. Bacteria have different properties, so not everyone can adapt to our intestines. Despite its role in evolution, the intestine is not our main organ.
A lot of changes have happened to him throughout the evolution. At some point, the immune system appeared, which helped maintain balance inside the intestine, sorted good and bad bacteria. Then, for this organism, there were organs of movement and organs of perception of the world that reacted to light. Over time, the brain and circulatory system developed, transferring nutrients from the intestine through the body. The brain developed, and we began to perceive ourselves and decided that the brain is the main thing, but we forgot about the intestines. This evolutionary process has been going on for millions of years, but at the same time, technology has been evolving for the last 100-120 years. Thanks to these technologies and the study of the human genome, we remembered the importance of the intestine. By the year 2000, humans had developed the technology to read the genetic sequence of a human cell, but the technology has side effects. One of the byproducts of reading the human genome is the emergence of technology for cheap reading of any DNA sequences.
At the end of the XX century, scientists thought that they had grown and studied all the microbes that exist. To study, a smear was taken from any surface, then this cotton swab was placed in a nutrient medium. That's how scientists found out what bacteria were there. After such studies, DNA reading technologies appeared, with the help of which the composition of not only microbes, but also DNA was recognized. New technologies have shown that there are many DNA microbes in the environment that have not been studied. Simultaneously with this discovery, it was found out that many unknown microbes also live in our intestines – the dark matter of microbes (English microbial dark matter). The evolution of technology has led us to the fact that it is now possible to detect and identify any microbes.
After the advent of new technologies, scientists did not immediately turn to intestinal microbes, because they began to observe diseases that greatly progressed in the XX century. One of these diseases is obesity. Studying obesity, American researchers began to compare microbes of people with low body weight and high body weight. It turned out that the microbes in the two groups differ. This is not proof that the microbiota is associated with obesity. To test the evidence, microbes were taken from obese people and transplanted into model animals. At the same time, microbes were taken from people without obesity and transplanted into model animals. All animals were fed a high-calorie diet. According to the results of the study, it turned out that model animals that carry the microbes of obese people gain weight much faster. This proved that the microbiota is associated with the disease. We have found microbes, we have shown that they are associated with certain diseases, but this is not a reason to call it a new organ.
The next stage was the study of microbes from the point of view of their importance for the body and intestines. The surface area of our skin is 2 square meters. The surface area of all our internal organs and mucosa is 400 square meters. If you imagine all the inflammations that appear on the skin, then their area will be about 2 square meters. We often wash and clean these meters, and they are in the fresh air, being dry. Imagine 400 square meters, always wet. All these meters are inside our body, which means in the dark. In such a nutrient medium, bacteria will multiply endlessly until the food runs out. These 400 square meters are a welcome piece for our bacteria. Since the appearance of the first intestine, we have become a more tasty morsel for bacteria, because we have a high body temperature and we are actively moving. The food we eat is good for bacteria, and the blood carries nutrients throughout the body. The main mechanism for maintaining cleanliness and order in these 400 square meters is the immune system. On the part of the bacterial kingdom, these are some of our symbiotic bacteria that live on this surface.
If we look at the epidemic diseases that grew in the XX century, we will notice that most of these diseases are non-communicable – diseases associated with dysfunction of the immune system. Today, these are only autoimmune diseases: metabolic syndrome, obesity and diabetes. The immune system, which binds the whole body, began to work worse in the XX century. There are more diseases. If you look closely at the changes in the immune system, it turns out that microbes have suffered the most as a result of these changes. The changes affected the way of eating. During the XX century, nutrition has changed a lot. The good microbes started getting less nutrition, and the bad ones got more of the food they love. At one point, antibiotics became the salvation, which stopped many infections, but the property of these molecules is that they kill both good and bad microbes. If we take antibiotics, then good microbes cannot maintain cleanliness in our body, and an unaffordable load falls on the immune system. In addition to changes in the diet itself, a huge amount of preservatives, herbicides, and pesticides have appeared in our food. These additives affect our micro-kingdom, so there are microbes in the body that are able to mutate quickly. These are not the best representatives. I would like to have a variety of bacteria on our 400 square meters, 50-70% of which are in our intestines. Scientists have begun to consider microbes on the entire area of our body as a separate organ called the microbiota. But only bacteria belong to this organ, and the interaction of bacteria with their environment is called the "microbiome".
About the author:
Dmitry Alekseev is an associate professor at the Institute of Aging (Groningen), Candidate of Biological Sciences.
Portal "Eternal youth" http://vechnayamolodost.ru